Ariel is the M4 mission of the ESA’s Cosmic Vision Program 2015-2025, whose aim is to characterize by lowresolution transit spectroscopy the atmospheres of over one thousand warm and hot exoplanets orbiting nearby stars. It has been selected by ESA in March 2018 and adopted in November 2020 to be flown, then, in 2029. It is the first survey mission dedicated to measuring the chemical composition and thermal structures of the atmospheres of hundreds of transiting exoplanets, in order to enable planetary science far beyond the boundaries of the Solar System. The Payload (P/L) is based on a cold section (PLM – Payload Module) working at cryogenic temperatures and a warm section, located within the Spacecraft (S/C) Service Vehicle Module (SVM) and hosting five warm units operated at ambient temperature (253-313 K). The P/L and its electrical, electronic and data handling architecture has been designed and optimized to perform transit spectroscopy from space during primary and secondary planetary eclipses in order to achieve a large set of unbiased observations to shed light and fully understand the nature of exoplanets atmospheres, retrieving information about planets interior and determining the key factors affecting the formation and evolution of planetary systems.
The most recent study of the Wide Field Infrared Survey Telescope (WFIRST) mission is based on reuse of an
existing 2.4m telescope. This study was commissioned by NASA to examine the potential science return and cost
effectiveness of WFIRST by using this significantly larger aperture telescope. We review the science program
envisioned by the WFIRST 2012-2013 Science Definition Team (SDT), an overview of the mission concept, and
the telescope design and status. Comparisons against the previous 1.3m and reduced cost 1.1m WFIRST design
concepts are discussed. A significant departure from past point designs is the option for serviceability and the
geostationary orbit location which enables servicing and replacement instrument insertion later during mission
life. Other papers at this conference provide more in depth discussion of the wide field instrument and the optional
exoplanet imaging coronagraph instrument.
The Space Interferometry Mission (SIM) has some very tight stability requirements that drive the thermal control approach well beyond the traditional spacecraft thermal control regime. The precision support structure will be constructed of composite materials with a quite low coefficient of thermal expansion (CTE) on the order of 10-7/K. Even then, the temperature variations of the structure cannot exceed about 0.2°C. For the main optical elements, which will be fabricated of ultra-low expansion glass, the temperature stability must be such that the temperature gradient through the glass cannot vary by more than a couple of millikelvin through the 5 cm thickness over a one hour period. The laser metrology system, which measures motions on the order of a few tens of picometers, contains some sensitive optical elements whose temperature variations cannot exceed a few tens of microkelvin. This paper will describe how the SIM thermal control designers have addressed some of these very challenging requirements.
The Precision Structure Subsystem (PSS) for the Space Interferometry Mission (SIM) is a large composite structure designed to house the interferometer optics in a structurally and thermally stable environment on orbit. The resulting design requirements of the PSS must be weighed against the demands of the baseline launch vehicle: the Space Shuttle. While a Shuttle launch provides new opportunities for the mission, it also presents new challenges. Many of these chal-lenges are reflected in the design of the PSS, including structural stability for supporting the optics on orbit, launch vehi-cle interface considerations (acoustic and stress loads), minimization of launch mass to provide maximum payload to orbit, thermal control to achieve necessary structural stability and a stable thermal environment for the optics, and isola-tion of the optics mounts from jitter sources and microdynamics effects. Many of these design challenges result in inherently conflicting requirements on the design of the PSS. Drawing on our experience with large composite structures such as the Chandra X-ray Observatory, TRW has created a conceptual design for this structure that addresses these challenging requirements. This paper will describe that conceptual design including trades and analyses that led to the design.
In 2009, NASA's Origins Program will launch the Space Interferometry Mission (SIM), a 10-meter-baseline optical interferometry instrument, into an Earth-trailing solar orbit. This instrument will be comprised of four parallel optical interferometers whose prime mission objective is to perform astrometric measurements at unprecedented accuracy. Launched by the Space Shuttle and boosted into its final trajectory by an integral propulsion system, SIM will collect data for more than five years in the search for extra-solar system planets.
NASA has assembled an integrated Jet Propulsion Laboratory (JPL)/Industry team comprised of TRW, Lockheed Martin, and Caltech to formulate a reference design to meet the SIM science objectives. Addressing unique technical challenges has proven to be a formidable task in numerous aspects of the system definition, from component development to system-level integration and test. Parallel activities to develop and test the necessary enabling technologies for SIM are coupled with the ongoing flight system design. The flight system design poses unique challenges in many areas, including geometric aspects of the layout, stability of the precision structure, thermal control, active vibration suppression, picometer-level laser metrology, etc. System-level trade studies that balance the requirements of the optics and metrology layouts and develop clean interfaces are presented herein. This paper also addresses the issues of the System Engineering processes and validation of performance specifications. Finally, this paper describes the current status of the SIM Reference System design.
The Space Interferometry Mission (SIM) will perform astrometry to a resolution of a few micro arc seconds. The development of this mission is being led by the California Institute of Technology, JPL for the National Aeronautics and Space Administration. A recent trade study was performed to compare two significantly different architectures. This paper will describe the two configurations and contrast some of their differences and similarities.
This study was undertaken at the JPL to identify salient features of two competing instrument designs and to select the design that best meets the goals of the Space Interferometry Mission. Features were examined in terms of meeting performance, cost, schedule and risk requirements. The study included the spacecraft, the space environment, metrology considerations, stabilization of optics with temperature, spacecraft structure, complexity, and end-to- end testing among other items. The most significant determinant was the fundamental implementation of the instrument's metrology system. The impact on the testbed program associated with the mission was considered the second most important issue. An error propagation formalism was developed to address various instrument geometries examined as part of this study. The formalism propagates metrology errors from the gauge readings through to the angle on the sky. An introduction to the formalism is presented.
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